Without limiting the scope of the invention, its background is described in connection with the compositions and compounds for oil recovery applications.
United States Patent Application No. 20080312108 (Berger and Berger, 2008) discloses compositions and process for recovering of oil from subterranean oil-bearing reservoirs consisting of green non-toxic biodegradable strong alkali metal salt of polymerized weak acids, one or more surfactants, an aqueous fluid, and optionally one or more mobility control agents and optionally one or more co-solvents. Such compositions are injected into the reservoir through one or more injection wells and assist in recovering trapped oil through one or more producing wells. The compositions and the process described in the invention offer the advantage of improved compatibility with unsoftened waters, surfactants, and various mobility control agents. The green non-toxic, biodegradable properties of the alkali makes it particularly suitable for environmentally sensitive applications such as offshore and inland lakes
U.S. Pat. No. 4,004,638 issued to Burdyn et al. (1977) teaches recovery of oil from subterranean oil reservoirs by water flooding employing an alkaline agent and a sulfonate surfactant. An aqueous initiation slug containing an alkaline agent selected from the group consisting of alkali metal and ammonium hydroxides is injected into the reservoir via a suitable injection system. Thereafter an aqueous surfactant slug is injected into the reservoir behind the initiation slug. The surfactant slug contains a sulfonate surfactant and an alkaline agent. Subsequent to injection of the surfactant slug, an aqueous flooding medium is injected in order to displace the oil within the reservoir to a production system from which it is recovered. A portion of the flooding medium may contain a thickening agent for mobility control purposes.
A large number of petroleum reservoirs have some hardness (divalent cations) in the water, and thus pose a great threat to the aqueous stability of the chemicals injected. Divalent cations precipitate with alkali, surfactant and polymer and result in plugging during injection. In addition, hardness has a dominant impact on phase behavior especially at low concentration of surfactant (Nelson, 1984) and this can cause high surfactant retention by ion exchange between the surfactant, brine, and clay (Hill, et al., 1977; Hirasaki, 1981). Therefore, extra measures are taken to test the compatibility of the injection chemicals with brine. One measure is softening of injection water, which is an expensive process that in some cases is not feasible.